During the past year the following studies were carried out: 1) The effects of dopamine receptor stimulating agents on tremor and involuntary movements in experimental monkeys. Either L-dopa in combination with 1-alpha-methyldopa hydrazine (MK-486) or 1-(2"-pyrimidyl)-4-piperonylpiperazine, an agent that stimulates dopamine receptors, relieves surgically induced tremor in monkeys and concomitantly evokes involuntary movements. These results indicate that tremor and involuntary movements are associated with a common mechanism and that the activity of the dopamine receptors is involved in the regulation of thse dysfunctions. 2) The effects of stimulation or blockade of dopamine receptors on dopamine biosynthesis in striatum. The blockade of dopamine receptors with Haloperidol results in an enhancement while the activation of dopamine receptors with Trivastal results in an inhibition of dopamine synthesis in striatal slices. c-AMP stimulates dopamine synthesis in striatal slices and it may play a role in the regulation of catecholamine synthesis. The relationship, if any, between dopamine receptor activity and c-AMP-induced stimulation of dopamine synthesis is now under investigation.